Czech J. Anim. Sci., 2024, 69(3):89-101 | DOI: 10.17221/158/2023-CJAS

The nurse sow system ‒ A natural process of handling large litters: A reviewReview

Joab Malanda Osotsi1,2, Gabriella Novotni-Danko1, Peter Balogh3
1 Department of Animal Science, Institute of Animal Science Biotechnology and Natural Conservation, Faculty of Agricultural and Food Sciences and Environmental Management, University of Debrecen, Debrecen, Hungary
2 Doctoral School of Animal Science, University of Debrecen, Debrecen, Hungary
3 Non-independent Department of Research Methodology and Statistics, Institute of Statistics and Methodology, Faculty of Economics and Business, University of Debrecen, Debrecen, Hungary

Reproductive performance in pig production has gained genetic momentum resulting in large litters. Several strategies have been used to raise the number of piglets to address the challenge of a large litter size. This review provides a rationale for employing the nurse sow system as a biological way of handling large litters, exploring its step-by-step processes and its selected impacts. By exposing these steps, pig farmers will use the information to pinpoint their weak points in the chain and customize the procedures to meet their farm-specific goals for improved productivity. The nurse sow system helps to maximize pre-weaning survival by boosting the overall worth of low birth weight piglets. When piglets weaned per sow/year are used as a performance benchmark, nurse sows weaning double litters become economically advantageous. Extended time in lactation for nurse sows gives them an ample time for their uterus to involute before the next pregnancy. However, nurse sows lose their body reserves reflected in backfat thickness from high milk production. Prolonged confinement in lactation deteriorates the physical condition of nurse sows, resulting in leg ulcers and teat damage. Additionally, piglets are more distressed when taken away from their biological sow to a new sow.

Keywords: fostering; piglet; pig production; selection

Received: November 16, 2023; Accepted: March 13, 2024; Published: March 29, 2024  Show citation

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Osotsi JM, Novotni-Danko G, Balogh P. The nurse sow system ‒ A natural process of handling large litters: A review. Czech J. Anim. Sci. 2024;69(3):89-101. doi: 10.17221/158/2023-CJAS.
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References

  1. Agbokounou AM, Ahounou GS, Youssao Abdou Karim I, Mensah GA, Koutinhouin B, Hornick JL. Effect of cow colostrum on the performance and survival rate of local newborn piglets in Benin Republic. Trop Anim Health Prod. 2017 Feb;49(2):287-94. Go to original source... Go to PubMed...
  2. Alexopoulos JG, Lines DS, Hallett S, Plush KJ. A review of success factors for piglet fostering in lactation. Animals (Basel). 2018 Mar 9;8(3):38. Go to original source... Go to PubMed...
  3. Algers B, Uvnas-Moberg K. Maternal behavior in pigs. Horm Behav. 2007 Jun;52(1):78-85. Go to original source... Go to PubMed...
  4. Alvasen K, Hansson H, Emanuelson U, Westin R. Animal welfare and economic aspects of using nurse sows in Swedish pig production. Front Vet Sci. 2017 Dec 1;4:204. Go to original source... Go to PubMed...
  5. Amdi C, Moustsen VA, Oxholm LC, Baxter EM, Sorensen G, Eriksson KB, Diness LH, Nielsen MF, Hansen CF. Comparable cortisol, heart rate and milk let-down in nurse sows and non-nurse sows. Livest Sci. 2017 Apr 1;198:174-81. Go to original source...
  6. Arnaud EA, Gardiner GE, Lawlor PG. Selected nutrition and management strategies in suckling pigs to improve post-weaning outcomes. Animals (Basel). 2023 Jun 15;13(12):1998. Go to original source... Go to PubMed...
  7. Barnett JL, Hemsworth PH, Cronin GM, Jongman EC, Hutson GD. A review of the welfare issues for sows and piglets in relation to housing. Aust J Agri Res. 2001 Aug 18;52(1):1-28. Go to original source...
  8. Baxter EM, Rutherford KMD, D'Eath RB, Arnott G, Turner SP, Sandoe P, Moustsen VA, Thorup F, Edwards SA, Lawrence A. The welfare implications of large litter size in the domestic pig II: Management factors. Anim Welfare. 2013 May;22(2):219-38. Go to original source...
  9. Berkeveld M, Langendijk P, Soede NM, Kemp B, Taverne MA, Verheijden JH, Kuijken N, Koets AP. Improving adaptation to weaning: Effect of intermittent suckling regimens on piglet feed intake, growth, and gut characteristics. J Anim Sci. 2009 Oct;87(10):3156-66. Go to original source... Go to PubMed...
  10. Bjorkman S, Oliviero C, Rajala-Schultz PJ, Soede NM, Peltoniemi OAT. The effect of litter size, parity and farrowing duration on placenta expulsion and retention in sows. Theriogenology. 2017 Apr 1;92:36-44. Go to original source... Go to PubMed...
  11. Bortolozzo FP, Zanin GP, Ulguim RDR, Mellagi APG. Managing reproduction in hyperprolific sow herds. Animals (Basel). 2023 Jun 1;13(11):1842. Go to original source... Go to PubMed...
  12. Bracke MBM, Hopster H. Assessing the importance of natural behavior for animal welfare. J Agric Environ Ethics. 2006 Feb;19:77-89. Go to original source...
  13. Bruun TS, Amdi C, Vinther J, Schop M, Strathe AB, Hansen CF. Reproductive performance of "nurse sows" in Danish piggeries. Theriogenology. 2016 Sep 1;86(4):981-7. Go to original source... Go to PubMed...
  14. Cabrera RA, Lin X, Campbell JM, Moeser AJ, Odle J. Influence of birth order, birth weight, colostrum and serum immunoglobulin G on neonatal piglet survival. J Anim Sci Biotechnol. 2012 Dec 23;3(1):42. Go to original source... Go to PubMed...
  15. Calderon Diaz JA, Diana A, Boyle LA, Leonard FC, McElroy M, McGettrick S, Moriarty J, Garcia Manzanilla E. Delaying pigs from the normal production flow is associated with health problems and poorer performance. Porcine Health Manag. 2017 Jul 5;3:13. Go to original source... Go to PubMed...
  16. Camerlink I, Farish M, D'Eath RB, Arnott G, Turner SP. Long term benefits on social behaviour after early life socialization of piglets. Animals (Basel). 2018 Oct 29;8(11):192. Go to original source... Go to PubMed...
  17. Clouard C, Resmond R, Prunier A, Tallet C, Merlot E. Exploration of early social behaviors and social styles in relation to individual characteristics in suckling piglets. Sci Rep. 2022 Feb 10;12(1):2318. Go to original source... Go to PubMed...
  18. Craig AL, Muns R, Gordon A, Magowan E. Extended nursing and/or increased starter diet al.owances for low weaning weight pigs. Asian-Australas J Anim Sci. 2020 Aug;33(8):1301-9. Go to original source... Go to PubMed...
  19. Cronin GM, Barnett JL, Hodge FM, Smith JA, McCallum TH. The welfare of pigs in two farrowing/lactation environments: Cortisol responses of sows. Appl Anim Behav Sci. 1991 Nov 1;32(2-3):117-27. Go to original source...
  20. Curtasu MV, Theil PK, Hedemann MS. Metabolomic profiles of colostrum and milk from lactating sows. J Anim Sci. 2016 Sep 1;94(3):272-5. Go to original source...
  21. Dall'Olio S, Ribani A, Moscatelli G, Zambonelli P, Gallo M, Nanni CL, Fontanesi L. Teat number parameters in Italian Large White pigs: Phenotypic analysis and association with vertnin (VRTN) gene allele variants. Livest Sci. 2018 Apr 1;210:68-72. Go to original source...
  22. De Passille AMB, Rushen J, Hartcosk TG. Ontogeny of teat fidelity in pigs and its relation to competition at suckling. Can J Anim Sci. 1988 Jun 1;68(2):325-38. Go to original source...
  23. De Vos M, Huygelen V, Willemen S, Fransen E, Casteleyn C, Van Cruchten S, Michiels J, Van Ginneken C. Artificial rearing of piglets: Effects on small intestinal morphology and digestion capacity. Livest Sci. 2014 Jan 1;159:165-73. Go to original source...
  24. Decaluwe R, Maes D, Declerck I, Cools A, Wuyts B, De Smet S, Janssens GP. Changes in back fat thickness during late gestation predict colostrum yield in sows. Animal. 2013 Dec;7(12):1999-2007. Go to original source... Go to PubMed...
  25. Decaluwe R, Maes D, Wuyts B, Cools A, Piepers S, Janssens GPJ. Piglets' colostrum intake associates with daily weight gain and survival until weaning. Livest Sci. 2014 Apr 1;162:185-92. Go to original source...
  26. Declerck I, Dewulf J, Sarrazin S, Maes D. Long-term effects of colostrum intake in piglet mortality and performance. J Anim Sci. 2016 Apr;94(4):1633-43. Go to original source... Go to PubMed...
  27. Deen MGH, Bilkei G. Cross fostering of low-birthweight piglets. Livest Prod Sci. 2004 Nov 1;90(2-3):279-84. Go to original source...
  28. Devillers N, Farmer C, Le Dividich J, Prunier A. Variability of colostrum yield and colostrum intake in pigs. Animal. 2007 Aug;1(7):1033-41. Go to original source... Go to PubMed...
  29. Devillers N, Le Dividich J, Prunier A. Influence of colostrum intake on piglet survival and immunity. Animal. 2011 Aug;5(10):1605-12. Go to original source... Go to PubMed...
  30. Duijvesteijn N, Veltmaat JM, Knol EF, Harlizius B. High-resolution association mapping of number of teats in pigs reveals regions controlling vertebral development. BMC Genomics. 2014 Jun 30;15(1):542. Go to original source... Go to PubMed...
  31. Dwyer CM. Maternal behaviour and lamb survival: From neuroendocrinology to practical application. Animal. 2014 Jan;8(1):102-12. Go to original source... Go to PubMed...
  32. Faccin JEG, Tokach MD, Goodband RD, DeRouchey JM, Woodworth JC, Gebhardt JT. Gilt development to improve offspring performance and survivability. J Anim Sci. 2022 Jun 1;100(6):skac128. Go to original source... Go to PubMed...
  33. Freking BA, Lents CA, Vallet JL. Selection for uterine capacity improves lifetime productivity of sows. Anim Reprod Sci. 2016 Apr;167:16-21. Go to original source... Go to PubMed...
  34. Freyer G. Maximum number of total born piglets in a parity and individual ranges in litter size expressed as specific characteristics of sows. J Anim Sci Technol. 2018 May 21;60:1-7. Go to original source...
  35. Garrido-Mantilla J, Sanhueza J, Alvarez J, Culhane MR, Davies P, Allerson MW, Torremorell M. Impact of nurse sows on influenza A virus transmission in pigs under field conditions. Prev Vet Med. 2021 Jan 17;188(1):105257. Go to original source... Go to PubMed...
  36. Horrell I, Hodgson J. The bases of sow-piglet identification. 1. The identification by sows of their own piglets and the presence of intruders. Appl Anim Behav Sci. 1992a Jun 1;33(4):319-27. Go to original source...
  37. Horrell I, Hodgson J. The bases of sow-piglet identifica-tion. 2. Cues used by piglets to identify their dam and home pen. Appl Anim Behav Sci. 1992b Jun 1;33(4):329-43. Go to original source...
  38. Hotzel MJ, Wolf FM, Dalla Costa OA. Behaviour of sows and piglets reared in intensive outdoor or indoor systems. Appl Anim Behav Sci. 2004 May 20;86(1-2):27-39. Go to original source...
  39. Houben MAM, Tobias TJ, Holstege MMC. The effect of double nursing, an alternative nursing strategy for the hyper-prolific sow herd, on herd performance. Porcine Health Manag. 2017 Feb 16;3:2. Go to original source... Go to PubMed...
  40. Cheng Z, Zhou ST, Zhang XH, Fu Q, Yang Y, Ji WB, Liu HG. Effects of early intermittent maternal separation on behavior, physiological, and growth performance in piglets. J Anim Sci. 2023 Jan 3;101:skad122. Go to original source... Go to PubMed...
  41. Iida R, Yatabe Y, Pineiro C, Koketsu Y. Nurse sows' reproductive performance in different parities and lifetime productivity in Spain. J Agric Sci. 2019 Jul 15;11(10):29-38. Go to original source...
  42. Jarvis S, D'Eath RB, Fujita K. Consistency of piglet crushing by sows. Anim Welfare. 2005 Feb;14(1):43-51. Go to original source...
  43. Jensen HE. Investigation into the pathology of shoulder ulcerations in sows. Vet Rec. 2009 Aug 8;165(6):171-4. Go to original source... Go to PubMed...
  44. Kanis E, De Greef KH, Hiemstra A, van Arendonk JA. Breeding for societally important traits in pigs. J Anim Sci. 2005 Apr;83(4):948-57. Go to original source... Go to PubMed...
  45. Kemp B, Da Silva CLA, Soede NM. Recent advances in pig reproduction: Focus on impact of genetic selection for female fertility. Reprod Domest Anim. 2018 Sep;53(Suppl_2):28-36. Go to original source... Go to PubMed...
  46. Kirkden RD, Broom DM, Andersen IL. Invited review: Piglet mortality: Management solutions. J Anim Sci. 2013 Jul;91(7):3361-89. Go to original source... Go to PubMed...
  47. Kirkwood RN, Langendijk P, Carr J. Management strategies for improving survival of piglets from hyperprolific sows. Thai J Vet Med. 2021 Dec;51(4):629-36. Go to original source...
  48. Klobasa F, Werhahn E, Butler JE. Regulation of humoral immunity in the piglet by immunoglobulins of maternal origin. Res Vet Sci. 1981 Sep;31(2):195-206. Go to original source...
  49. Klobasa F, Werhahn E, Butler JE. Composition of sow milk during lactation. J Anim Sci. 1987 May;64(5):1458-66. Go to original source... Go to PubMed...
  50. Knol EF, Leenhouwers JI, Van der Lende T. Genetic aspects of piglet survival. Livest Prod Sci. 2002 Nov 28;78(1):47-55. Go to original source...
  51. Knol EF, van der Spek D, Zak LJ. Genetic aspects of piglet survival and related traits: A review. J Anim Sci. 2022 Jun;100(6):skac190. Go to original source... Go to PubMed...
  52. Kobek-Kjeldager C, Moustsen VA, Theil PK, Pedersen LJ. Managing large litters: Selected measures of performance in 10 intermediate nurse sows and welfare of foster piglets. Appl Anim Behav Sci. 2020 Dec 1;233:105149. Go to original source...
  53. Koketsu Y, Tani S, Iida R. Factors for improving reproductive performance of sows and herd productivity in commercial breeding herds. Porcine Health Manag. 2017Jan 9;3:1. Go to original source... Go to PubMed...
  54. Koketsu Y. Longevity and efficiency associated with age structures of female pigs and herd management in commercial breeding herds. J Anim Sci. 2007 Apr;85(4):1086-91. Go to original source... Go to PubMed...
  55. Lawrence AB, Terlouw EM. A review of behavioral factors involved in the development and continued performance of stereotypic behaviors in pigs. J Anim Sci. 1993 Oct;71(10):2815-25. Go to original source... Go to PubMed...
  56. Lay DC, Matteri RL, Carroll J, Fangman TJ, Safranski TJ. Preweaning survival in swine. J Anim Sci. 2002 Jan 1;80:74-86.
  57. Le Dividich J, Rooke JA, Herpin P. Nutritional and immunological importance of colostrum for the new-born pig. J Agric Sci. 2005 Oct 31;143(6):469-85. Go to original source...
  58. Lopez-Moreno G, Schmitt C, Spronk T, Culhane M, Torremorell M. Evaluation of internal farm biosecurity measures combined with sow vaccination to prevent influenza A virus infection in groups of due-to-wean pigs. BMC Vet Res. 2022 Nov 9;18(1):393. Go to original source... Go to PubMed...
  59. Lucas ME, Hemsworth LM, Hemsworth PH. Review: Early life piglet experiences and impacts on immediate and longer-term adaptability. Animal. 2023 Jun 22:100889. Go to original source... Go to PubMed...
  60. Lund MS, Puonti M, Rydhmer L, Jensen J. Relationship between litter size and perinatal and pre-weaning survival in pigs. J Anim Sci. 2002 Apr;74(2):217-22. Go to original source...
  61. Milligan BN, Fraser D, Kramer DL. Birth weight variation in the domestic pig: Effects on offspring survival, weight gain and suckling behaviour. Appl Anim Behav Sci. 2001 Aug 1;73(3):179-91. Go to original source... Go to PubMed...
  62. Muns R, Nuntapaitoon M, Tummaruk P. Non-infectious causes of pre-weaning mortality in piglets. Livest Sci. 2016 Feb;184:46-57. Go to original source...
  63. Norris D, Ngambi JW, Mabelebele M, Alabi OJ, Benyi K. Genetic selection for docility: A review. J Anim Plant Sci. 2014 Jan 1;24(2):374-9.
  64. Novotni-Danko G, Balogh P, Huzsvai L, Gyori Z. Effect of feeding liquid milk supplement on litter performances and on sow back-fat thickness change during the suckling period. Arch Anim Breed. 2015 Jun 29;58(1):229-35. Go to original source...
  65. Nowak B, Mucha A, Moska M, Kruszynski W. Reproduction indicators related to litter size and reproduction cycle length among sows of breeds considered maternal and paternal components kept on medium-size farms. Animals (Basel). 2020 Jul 9;10(7):1164. Go to original source... Go to PubMed...
  66. Oliviero C, Junnikkala S, Peltoniemi O. The challenge of large litters on the immune system of the sow and the piglets. Reprod Domest Anim. 2019 Sep;54(Suppl_3):12-21. Go to original source... Go to PubMed...
  67. Oliviero C. Offspring of hyper prolific sows: Immunity, birthweight, and heterogeneous litters. Mol Reprod Dev. 2023 Jul;90(7):580-4. Go to original source... Go to PubMed...
  68. Patterson J, Foxcroft G. Gilt management for fertility and longevity. Animals (Basel). 2019 Jul 9;9(7):434. Go to original source... Go to PubMed...
  69. Pearson JM, Pajor EA, Caulkett NA, Levy M, Campbell JR, Windeyer MC. Benchmarking calving management practices on western Canada cow-calf operations. Transl Anim Sci. 2019 Jun 26;3(4):1446-59. Go to original source... Go to PubMed...
  70. Peltoniemi O, Han T, Yun J. Coping with large litters: Management effects on welfare and nursing capacity of the sow. J Anim Sci Technol. 2021 Mar;63(2):199-210. Go to original source... Go to PubMed...
  71. Pettigrew JE, Cornelius SG, Eidman VR, Moser RL. Integration of factors affecting sow efficiency: A modeling approach. J Anim Sci. 1986 Oct;63(4):1314-21. Go to original source... Go to PubMed...
  72. Pokorna K, Citek J, Zadinova K, Okrouhla M, Lebedova N, Komosny M, Stupka R. Influence of the use of nurse sows on their lifetime performance. Czech J Anim Sci. 2020 Mar 31;65(3):97-103. Go to original source...
  73. Portele K, Scheck K, Siegmann S, Feitsch R, Maschat K, Rault JL, Camerlink I. Sow-piglet nose contacts in free-farrowing pens. Animals (Basel). 2019 Jul 31;9(8):513. Go to original source... Go to PubMed...
  74. Prunier A, Heinonen M, Quesnel H. High physiological demands in intensively raised pigs: Impact on health and welfare. Animal. 2010 Jun;4(6):886-98. Go to original source... Go to PubMed...
  75. Quesnel H, Farmer C, Devillers N. Colostrum intake: Influence on piglet performance and factors of variation. Livest Sci. 2012 Jul 1;146(2-3):105-14. Go to original source...
  76. Quiniou N, Dagorn J, Gaudre D. Variation of piglets' birth weight and consequences on subsequent performance. Livest Prod Sci. 2002 Nov 28;78(1):63-70. Go to original source...
  77. Rezac I, Kernerova N, Komosny M, Kunes R, Havrdova N, Poborska A, Polivkova D, Kantor M, Zabransky L. Possibilities for dealing with large litters of piglets. J Cent Eur Agric. 2023 Mar 29;24(1):61-71. Go to original source...
  78. Robinson JA, Buhr MM. Impact of genetic selection on management of boar replacement. Theriogenology. 2005 Jan 15;63(2):668-78. Go to original source... Go to PubMed...
  79. Rolinec M, Biro D, Galik B, Simko M, Juracek M. Immunoglobulins in colostrum of sows with porcine reproductive and respiratory syndrome-PRRS. J Cent EurAgric. 2012 Jun 18;13(2):303-11. Go to original source...
  80. Rutherford KM, Baxter EM, Death RB, Turner SP, Arnott G, Roehe R, Ask B, Sandoe P, Moustsen VA, Thorup F, Edwards SA. The welfare implications of large litter size in the domestic pig I: Biological factors. Anim Welfare. 2013 May 1;22(2):199-218. Go to original source...
  81. Rzezniczek M, Gygax L, Wechsler B, Weber R. Comparison of the behaviour of piglets raised in an artificial rearing system or reared by the sow. Appl Anim Behav Sci. 2015 Apr 1;165:57-65. Go to original source...
  82. Safranski TJ. Genetic selection of boars. Theriogenology. 2008 Nov;70(8):1310-6. Go to original source... Go to PubMed...
  83. Salazar LC, Ko HL, Yang CH, Llonch L, Manteca X, Camerlink I, Llonch P. Early socialisation as a strategy to increase piglets' social skills in intensive farming conditions. Appl Anim Behav Sci. 2018 Sep 1;206:25-31. Go to original source...
  84. Sasaki Y, Koketsu Y. Sows having high lifetime efficiency and high longevity associated with herd productivity in commercial herds. Livest Sci. 2008 Oct 1;118(1-2):140-6. Go to original source...
  85. Schild SL, Baxter EM, Pedersen LJ. A review of neonatal mortality in outdoor organic production and possibilities to increase piglet survival. Appl Anim Behav Sci. 2020 Oct 1;231: 105088. Go to original source...
  86. Schmitt O, Baxter EM, Boyle LA, O'Driscoll K. Nurse sow strategies in the domestic pig: I. Consequences for selected measures of sow welfare. Animal. 2019 Mar;13(3):580-9. Go to original source... Go to PubMed...
  87. Skok J, Gerken M. Suckling strategies in the pig: The Gottingen minipig as a model. Livest Sci. 2016 Feb 1;184:78-84. Go to original source...
  88. Sola-Oriol D, Gasa J. Feeding strategies in pig production: Sows and their piglets. Anim Feed Sci Technol. 2017 Nov 1;233:34-52. Go to original source...
  89. Sorensen JT, Rousing T, Kudahl AB, Hansted HJ, Pedersen LJ. Do nurse sows and foster litters have impaired animal welfare? Results from a cross-sectional study in sow herds. Animal. 2016 Apr;10(4):681-6. Go to original source... Go to PubMed...
  90. Spinka M. How important is natural behaviour in animal farming systems? Appl Anim Behav Sci. 2006 Oct 1;100(1-2):117-28. Go to original source...
  91. Strathe AV, Bruun TS, Hansen CF. Sows with high milk production had both a high feed intake and high body mobilization. Animal. 2017 Nov;11(11):1913-21. Go to original source... Go to PubMed...
  92. Theil PK, Krogh U, Bruun TS, Feyera T. Feeding the modern sow to sustain high productivity. Mol Reprod Dev. 2023 Jul;90(7):517-32. Go to original source... Go to PubMed...
  93. Thiengpimol P, Koonawootrittriron S, Suwanasopee T. Genetic and phenotypic correlations between backfat thickness and weight at 28 weeks of age, and reproductive performance in primiparous Landrace sows raised under tropical conditions. Trop Anim Health Prod. 2022 Jan 11;54(1):43. Go to original source... Go to PubMed...
  94. Thorsen CK, Schild SL, Rangstrup-Christensen L, Bilde T, Pedersen LJ. The effect of farrowing duration on maternal behavior of hyperprolific sows in organic outdoor production. Livest Sci. 2017 Oct 1;204:92-7. Go to original source...
  95. van Nieuwamerongen SE, Bolhuis JE, van der Peet-Schwering CM, Soede NM. A review of sow and piglet behaviour and performance in group housing systems for lactating sows. Animal. 2014 Mar;8(3):448-60. Go to original source... Go to PubMed...
  96. Vanheukelom V, Driessen B, Geers R. The effects of environmental enrichment on the behaviour of suckling piglets and lactating sows. A review. Livest Sci. 2012 Feb 1;143(2-3):116-31. Go to original source...
  97. Vinsky MD, Novak S, Dixon WT, Dyck MK, Foxcroft GR. Nutritional restriction in lactating primiparous sows selectively affects female embryo survival and overall litter development. Reprod Fertil Dev. 2006;18(3):347-55. Go to original source... Go to PubMed...
  98. Ward SA, Kirkwood RN, Plush KJ. Are larger litters a concern for piglet survival or an effectively manageable trait? Animals (Basel). 2020 Feb 17;10(2):309. Go to original source... Go to PubMed...
  99. Weary DM, Appleby MC, Fraser D. Responses of piglets to early separation from the sow. Appl Anim Behav Sci. 1999 Apr 30;63(4):289-300. Go to original source...
  100. Weber R, Keil NM, Fehr M, Horat R. Factors affecting piglet mortality in loose farrowing systems on commercial farms. Livest Sci. 2009 Sep 1;124(1-3):216-22. Go to original source...
  101. Yun J, Han T, Bjorkman S, Nysten M, Hasan S, Valros A, Oliviero C, Kim Y, Peltoniemi O. Factors affecting piglet mortality during the first 24 h after the onset of parturition in large litters: Effects of farrowing housing on behaviour of postpartum sows. Animal. 2019 May;13(5):1045-53. Go to original source... Go to PubMed...
  102. Zak LJ, Gaustad AH, Bolarin A, Broekhuijse MLWJ, Walling GA, Knol EF. Genetic control of complex traits, with a focus on reproduction in pigs. Mol Reprod Dev. 2017 Sep;84(9):1004-11. Go to original source... Go to PubMed...
  103. Zeng ZK, Urriola PE, Dunkelberger JR, Eggert JM, Vogelzang R, Shurson GC, Johnston LJ. Implications of early-life indicators for survival rate, subsequent growth performance, and carcass characteristics of commercial pigs. J Anim Sci. 2019 Jul 30;97(8):3313-25. Go to original source... Go to PubMed...
  104. Zurbrigg K. Sow shoulder lesions: Risk factors and treatment effects on an Ontario farm. J Anim Sci. 2006 Sep;84(9):2509-14. Go to original source... Go to PubMed...

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